1 Overview

1.1 Introduction

The QT1106 is an easy to use sensor IC based on

Quantum’s patented charge-transfer (‘QT’) principles for

robust operation and ease of design. This device has many

advanced features which provide for reliable, trouble-free

operation over the life of the product. In particular the

QT1106 features advanced self-calibration, drift

compensation, and fast thermal tracking. Unlike prior

devices, the QT1106 can tolerate power supply fluctua tions

better in order to eliminate the need for a voltage regulator in

many cases.

1.2 Burst Operation

The device operates in burst mode. Each key is acquired

using a burst of charge-transfer sensing pulses whose count

varies depending on the value of the sense capacitor Cs and

the load capacitance Cx (finger touch capacitance and circuit

stray capacitance).

The channels’ signals are acquired using three successive

bursts of pulses:

Burst 1: B1, B3, B5, B7 (for discrete keys 1, 3, 5, 7)

Burst 2: B2, B4, B6 (for discrete keys 2, 4, 6 )

Burst 3: A1, A2, A3 (for wheel or slider)

Bursts always operate in 1, 2, 3 sequence as a group and

occur one right after the other with minimum delay. The

groups are separated by an interval of time that can be used

for SPI communications.

Spread-spectrum operation - Bursts can operate over a

spread of frequencies, so that external fields will have

minimal effect on key operation and emissions are very

weak.

Spread-spectrum operation works together with the ‘detect

integrator’ (DI) mechanism to dramatically reduce the

probability of false detection due to noise. An external RC

circuit is required to implement spread spectrum, but this

circuit is optional.

1.3 User Interface Layout Options

The QT1106 can sense through all common plastics or glass

or other dielectric materials up to 10mm thick. It can be used

to implement a linear slider or rotary scroll wheel plus seven

additional discrete keys. The slider or wheel indicat es

absolute positions.

1.4 Slider and Wheel Construction

The QT1106 can connect to either a wheel or a linear slider

element (Figure 1.1). Selection of wheel or linear operation

is set through an SPI command. The basis of these designs

is found in US Patent 4,264,903 (expired).

The first and last positions of the linear slider have larger

touch areas.

As with touch button electrodes, wheels and sliders can be

constructed as etched areas on a PCB or flex circuit, or from

clear conductors such as Indium Tin Oxide (ITO) or screen-

printed Orgacon™ (Agfa) to allow backlighting effects, or for

use over an LCD display.

1.5 QMagic

Channel 7 of the QT1106 can optionally operate a ‘magic on’

function based on hand or body proximity to a product. By

using a relatively large electrode inside the product’s

enclosure and a larger value of Csb7 (see Figure 2.1), the

product can auto power up or activate its display with hand

approach. This simple feature can add enormous sales

appeal to almost any product.

1.6 SPI Interface

The QT1106 uses a five-wire SPI interface. In addition to the

standard four SPI signals (/SS, SCLK, MOSI and MISO),

there is a DRDY (data ready) output for flow control.

The QT1106 also provides a CHANGE signal to indicate

when there has been a change in detection state. This

removes the need for the host to poll the QT1106

continuously.

On each SPI transfer the host sends three bytes to the

QT1106 and the QT1106 simultaneously sends three bytes

to the host. The bytes sent from the host provide the QT1106

with all its configuration information; the bytes sent from the

QT1106 convey the key states.

3

QT1106-ISG R8I.05/0906

Figure 1.1 All-Metal Slider and Wheel Construction

(downloadable example CAD files for wheels and sliders can be found on the Quantum

website,http://www.qprox.com/toolbox/1106 )

0

127

1 to 126

Position (at 7 bits - 0 to 127)

SNSA3

SNSA3

SNSA2

SNSA1

Tips of triangles should be

spaced <=4mm apart.

<=4mm

<=4mm

SNSA3

SNSA2

SNSA1

Position 0

Position 43

Position 85